Gremlins in my gauges!

[blue_bayou]

I have an 09 boat with triple DF300 motors and 5 SMIS 4" multi-gauges. It was repowered in '13 with new motors but the gauges and interface cables are original. All the batteries have been replaced in the last year with Odyssey AGM 1150 CCA. The motors have 850 hours.

I was away all summer and the boat was not run for 4 months. After returning back, on the first time out, I noticed on start-up that the gauges were flashing and not properly displaying RPM's. I turned off all motors and battery switches to reboot the system. I was able to get rpm displayed but gauges were still flashing. Upon running the boat, I noticed that the rpm's were not in sync, although the motors appeared to be. When dropping off plane, the gauges were all frozen at much higher rpm's. After running for an hour or so, the gauges appeared to normalize. The next outing, I had the same issues, but not in any particular order. The fuel gauges were also not properly reading fuel levels. It appeared that the inconsitencies were more apparent at higher rpm's. By the way, the engines are running great!

I would appreciate any opinions on what may be the problem, or where to start looking. Could a bad gauge cause this, or maybe an interface cable gone bad? Thanks for any insights.

[Moonlighter]

Although you have fairly new batteries, these kinds of problems may happen what there is poor voltage supply to the NMEA2000 network. The fact that things somewhat improved after an hour with the engines running also points towards that.

So I suggest that you inspect, clean and retighten all main battery connections, give the batteries a really good charge, and inspect the network power supply connections and fuse to make sure all connections/contacts are clean and tight.

[briscoe]

Here, here on cleaning those connections. I was having some issues that sounded the same. After removing the nuts and cleaning connectors and posts it went away.